It is known that a curved or arcuate flapper valve may be used in a subsurface well safety valve to provide a larger bore in the safety valve as compared to a flat flapper valve. Such valves as described in U.S. Pat. Nos. 2,162,578; 4,531,587; 4,854,387 are designed to provide larger bores and thus increase the well production through the valve. However, such valves were complicated to manufacture generally requiring a multi-axis mill and were quite expensive. Conventional curved flappers utilize a seat which required developing the seat line by two diameters. Furthermore, the prior art curved flapper valves, which were operated by a flow tube, retracted the flow tube away from the flapper in the closed position thereby increasing the length, expense and spring-operating parameter requirements.
The present invention is directed to an improved well safety valve having a curved flapper in which the flapper has a sealing surface on its interior or inside diameter and developed by one diameter as distinguished from valves having a seat surface developed by two diameters. Furthermore, the present valve includes a flow tube having a lower end contoured to coact with the flapper for reducing the overall length of the safety valve, reducing the required spring parameters, and thereby reducing the cost of the valve. Furthermore, the method of making the flapper of the present invention provides flappers by different manufacturing methods whereby the cost of the flapper is significantly reduced from curved flappers manufactured on multi-axis milling machines.